Power Saving in a Device Compatible with Cellular and WLAN Networks

ABSTRACT

A mobile communication device is able to communicate with wireless local area network and with a cellular network. A communication system is able to route a communication session between the mobile communication device and another communication device either by way of the wireless local area network or the cellular network. The communication system is able to trigger the mobile communication device via the cellular network to search for and attempt to connect to the wireless local area network. The mobile communication device, in response to reception of signaling via the cellular network, is able to activate a wireless local area network interface of the mobile communication device and to establish a connection to the wireless local area network.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/426,977 filed Jun. 28, 2006, entitled, “Power Saving in a DeviceCompatible with Cellular and WLAN Network”, which will issue on Nov. 9,2010 as U.S. Pat. No. 7,830,844, and which is incorporated by referencein its entirety.

BACKGROUND

Members of an enterprise may be provided with mobile stations that areable to communicate via both cellular networks and wireless local areanetworks (WLAN). While such a device is within the coverage area of anenterprise WLAN (eWLAN) or a public WLAN, a private branch exchange(PBX) of the enterprise may be able to route communication sessionsbetween the mobile device and other communication devices via the eWLANor the public WLAN, respectively. In addition, while such a device iswithin the coverage area of a cellular network, the PBX may be able toroute communication sessions between the mobile device and othercommunication devices via the cellular network.

There is a tradeoff between WLAN detection latency and the powerconsumption required of the mobile station, i.e., the power consumptiongoes up with the rate at which the WLAN radio is activated to search forWLAN access points (APs). Unfortunately good responsiveness is difficultto obtain without severely impacting the power consumption of the mobilestation. This problem is exacerbated by the fact that Institute ofElectrical and Electronic Engineers (IEEE) 802.11h has requirements forpassive scanning until the mobile station determines its currentregulatory jurisdiction. Passive scanning involves leaving the WLANradio on in receive mode long enough to ensure that any AP beacons willbe received with high probability. This is normally a much more powerintensive process than using active scanning. The power consumptionproblem will also worsen as the number of WLAN channels increases, whichwill happen as handsets are equipped with IEEE 802.11a radios.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments are illustrated by way of example and not limitation in thefigures of the accompanying drawings, in which like reference numeralsindicate corresponding, analogous or similar elements, and in which:

FIG. 1 is an illustration of an exemplary communications system,according to some embodiments of the invention;

FIG. 2 is a block diagram of an exemplary mobile station, according tosome embodiments of the invention;

FIG. 3 is a flowchart of an exemplary method for a mobile station toconnect to an Internet Protocol public branch exchange (PBX), accordingto embodiments of the invention;

FIG. 4 is a flowchart of an exemplary method in a mobility manager forestablishing a communication session with a mobile station, according toembodiments of the invention;

FIGS. 5 and 6 are a flowchart of an exemplary method in a mobile stationfor handling an incoming communication session, according to embodimentsof the invention; and

FIGS. 7 and 8 are a flowchart of an exemplary method in a mobile stationfor handling an outgoing communication session, according to embodimentsof the invention.

It will be appreciated that for simplicity and clarity of illustration,elements shown in the figures have not necessarily been drawn to scale.For example, the dimensions of some of the elements may be exaggeratedrelative to other elements for clarity.

DETAILED DESCRIPTION

In the following detailed description, numerous specific details are setforth in order to provide a thorough understanding of embodiments of theinvention. However it will be understood by those of ordinary skill inthe art that the embodiments of the invention may be practiced withoutthese specific details. In other instances, well-known methods,procedures, components and circuits have not been described in detail soas not to obscure the embodiments of the invention.

As explained hereinabove, searches for WLANs consume power. Embodimentsof the invention address this issue by allowing a mobile station to haveits WLAN interface in a lower power state and to be notified if itshould attempt to connect to a WLAN. The notification will be sent tothe mobile station via a cellular network.

A mobility manager maintains presence information of the mobile stationto keep track of whether the mobile station is currently associated witha WLAN. The mobility manager may trigger a mobile station via a cellularnetwork to search for and attempt to connect to a WLAN in order toreceive an incoming communication session. The WLAN may be an enterpriseWLAN or any other public or private WLAN. A particular mobile stationmay be able to connect to more than one WLAN at any given time and mayprefer connections with an eWLAN. The mobile station, in response toreception of signaling via the cellular network, is able to activate itswireless local area network interface and to establish a connection to aWLAN.

FIG. 1 is an illustration of an exemplary communications system 100,according to some embodiments of the invention. Communication system 100includes an enterprise communication system 102, a mobile station 104, aPSDN (packet switched data network) and/or PSTN (public switchingtelephone network) 106, a PLMN (public land mobile network) 108 coupledto PSDN/PSTN 106, a PLMN base station 110 coupled to PLMN 108,communication devices 112 and 113 coupled to PSDN/PSTN 106, and a WLANAP 111 coupled to PSDN 106.

Enterprise communication system 102 includes an eWLAN 114. Enterprisecommunication system 102 also includes a PSDN/PSTN gateway 116, an IPPBX (Internet protocol private branch exchange) 118, an enterprise dataserver (EDS) 119, and a mobility manager 120, all of which are connectedto an enterprise network 121. PSDN/PSTN gateway 116 couples PSDN/PSTN106 to enterprise network 121. Mobility manager 120 may be implementedin IP PBX 118 or elsewhere in system 102.

eWLAN 114 includes APs, for example, AP 122, and a wired infrastructure124. Wired infrastructure 124 is coupled to enterprise network 121. APsof eWLAN 114 may be connected to infrastructure 124 via wired and/orwireless links. eWLAN 114, or parts of eWLAN 114, may be a “mesh” WLAN,in which one or more APs are connected to infrastructure 124 indirectlythrough other APs. If eWLAN 114 or part of eWLAN 114 is a mesh WLAN,eWLAN 114 may include one or more mesh points. Wired links, mesh pointsand APs other than AP 122 are not shown in FIG. 1 as not to obscure thedescription of the embodiments of the invention.

In some embodiments, APs 111 and 122 and mobile station 104 are allcompatible with one or more of the IEEE 802.11 standards for WLAN MediumAccess Control (MAC) and Physical layer (PHY) specifications, or futurerelated standards.

However, it will be obvious to those of ordinary skill in the art how tomodify the following for any other WLAN communications in which a mobilestation and an access point can be associated or not associated.

If mobile station 104 is within a coverage area 126 of AP 122 and iswirelessly connected to AP 122, as shown with arrow 128, IP PBX 118and/or enterprise data server 119 may be able to communicate with mobilestation 104 by way of eWLAN infrastructure 124 and AP 122.

Mobile station 104 is able to communicate with AP 111. If mobile station104 is wirelessly connected to AP 111, as shown with arrow 115, IP PBX118 and/or enterprise data server 119 may be able to communicate withmobile station 104 by way of PSDN gateway 116, PSDN 106 and AP 111.

Mobile station 104 is able to communicate with PLMN base station 110using one or more cellular communication standards. If mobile station104 is wirelessly connected to PLMN base station 110, as shown witharrow 130, IP PBX 118 and/or enterprise data server 119 may be able tocommunicate with mobile station 104 by way of PSDN/PSTN gateway 116,PSDN/PSTN 106, PLMN 108 and PLMN base station 110.

Mobile station 104 may be configured, permanently or temporarily, tooperate in an “enterprise mode”. In enterprise mode, communications toand from mobile station 104 are routed to the appropriate entity insystem 102, for example, IP PBX 118 for voice communications, mobilitymanager 120 for signaling and EDS 119 for data communications, whichrepresent a local-to-the-enterprise sink/source for voice, signaling anddata communications, respectively. The communication may communicate anysuitable information, for example, any or any combination of signaling,voice, video and data.

Consider the following examples, where a caller who uses a deviceoutside of the enterprise places a call to the user of mobile station104.

In one example, the caller dials the main telephone number of theenterprise, followed by an extension number for the user. Device 112transmits a communication request to PSDN/PSTN 106 that includes anaccess code, e.g. the telephone number associated with enterprisecommunication system 102. PSDN/PSTN 106 routes the communication requestto IP PBX 118, where the caller hears a message such as “You havereached Company ABC. If you know the extension of the party you wish tocall, please enter it now.” The caller dials the extension number, anddevice 112 sends to IP PBX 118 another access code, e.g. the extensionnumber that is associated with mobile station 104. In response, IP PBX118 attempts to connect with mobile station 104.

In another example, the caller dials a direct number for the user ofmobile station 104. Device 112 transmits a communication request toPSDN/PSTN 106 that includes an access code, e.g. the telephone numberthat is associated with mobile station 104. PSDN/PSTN 106 routes thecommunication request to IP PBX 118 and IP PBX 118 attempts to connectwith mobile station 104.

Consider also the following examples, where a call takes place entirelyinside enterprise communication system 102, using extension numbersassigned by IP PBX 118.

In one example, a wired communication device 132 that is coupled to IPPBX 118 transmits a communication request to IP PBX 118 that includes anaccess code, e.g. an extension number of mobile station 104, and IP PBXattempts to connect with mobile station 104.

In another example, mobile station 104 transmits a communication requestto IP PBX 118 that includes an access code of a wireless communicationdevice 134 that is coupled to eWLAN infrastructure 124. In response, IPPBX 118 attempts to connect with device 134.

Similarly, incoming communication sessions destined for mobile station104 may originate at an external source such as communication device113, at a source internal to the enterprise such as a communicationdevice 135, or at a source internal to the eWLAN, such as wirelesscommunication device 134.

While in the enterprise, it may be more cost-effective for mobilestation 104 to communicate through eWLAN 114 rather than through PLMN108. While not in the enterprise, it may be more cost-effective formobile station 104 to communicate through AP 111 than through PLMN 108.However, as explained above, searching for a WLAN affects the powerconsumption of mobile station 104.

Mobile station 104 may provide presence signaling to mobility manager120 so that mobility manager 120 knows whether mobile station 104 iscurrently associated with an AP in eWLAN 114 or with AP 111.

If an incoming communication session for mobile station 104 arrives atIP PBX 118 and mobility manager 120 knows that mobile station 104 iscurrently connected to eWLAN 114 or AP 111, then mobility manager 120can direct IP PBX 118 to establish the communication session with mobilestation 104 through eWLAN 114 or AP 111, respectively.

However, if an incoming communication session for mobile station 104arrives at IP PBX 118 (or enterprise data server 119) and mobilitymanager 120 knows that mobile station 104 is currently not connected toeWLAN 114 and not to AP 111, then mobility manager 120 can signal mobilestation 104 via PLMN 108. In response, mobile station 104 can attempt toconnect to eWLAN 114 or AP 111, and if successful, then mobility manager120 can direct IP PBX 118 (or enterprise data server 119) to establishthe communication session with mobile station 104 through eWLAN 114 orAP 111, respectively. In this manner, mobile station 104 can enjoy anycost benefits of using eWLAN 114 or AP 111 for the communication sessionwithout having to consume power searching for a WLAN when no incoming oroutgoing communication sessions are being handled. In enterprise mode,mobile station 104 may refrain from searching for a WLAN when noincoming or outgoing communication sessions are being handled.

FIG. 2 is a block diagram of mobile station 104, according to someembodiments of the invention. Mobile station 104 includes a processor202, and a memory 204 coupled to processor 202. Memory 204 stores code206 that, when executed by processor 202, may implement the methodsdescribed herein.

Mobile station 104 includes a wireless communication interface 210,compatible with one or more standards of the family of IEEE 802.11wireless communication standards. Wireless communication interface 210is coupled to processor 202 and includes at least a baseband controller212, a radio 214, and an antenna 216.

Mobile station 104 includes a wireless communication interface 220,compatible with one or more wireless cellular communication standards.Wireless communication interface 220 is coupled to processor 202 andincludes at least a baseband controller 222, a radio 224, and an antenna226. Mobile station 104 includes other components that are not shown inFIG. 2 for clarity.

A non-exhaustive list of examples for mobile station 104 includes awireless-enabled laptop, a wireless-enabled cellphone, awireless-enabled personal digital assistant (PDA), a wireless-enabledsmart phone, a wireless-enabled video camera, a wireless-enabled gamingconsole, a wireless Internet Protocol (IP) phone and any other suitablemobile device.

A non-exhaustive list of examples for standards with which PSDN basestation 110 and mobile station 104 may communicate with includes DirectSequence-Code Division Multiple Access (DS-CDMA) cellular radiotelephonecommunication, Global System for Mobile Communications (GSM) cellularradiotelephone, North American Digital Cellular (NADC) cellularradiotelephone, Time Division Multiple Access (TDMA), Extended-TDMA(E-TDMA) cellular radiotelephone, wideband CDMA (WCDMA), General PacketRadio Service (GPRS), Enhanced Data for GSM Evolution (EDGE), 3G and 4 Gcommunication.

FIG. 3 is a flowchart of an exemplary method for mobile station 104 tocommunicate with mobility manager 120, according to embodiments of theinvention. As shown at 300, mobile station 104 may execute the method ofFIG. 3 as part of the transition into enterprise mode, for example,after mobile station 104 is powered up.

At 302, mobile station 104 activates communication interface 210 andscans for a WLAN. If, as checked at 304, mobile station 104 detects oneor more APs of eWLAN 114, for example, AP 122, then mobile station 104may connect to one of the detected APs and communicate through thedetected AP to mobility manager 120, as shown in 306. At 308, mobilestation 104 starts maintaining presence signaling with mobility manager120 via eWLAN 114.

If, as checked at 310, mobile station 104 does not detect any AP ofeWLAN 114 but does detect another WLAN, for example AP 111, then mobilestation 104 may connect to AP 111 and communicate through AP 111 tomobility manager 120, as shown in 312. At 314, mobile station 104 startsmaintaining presence signaling with mobility manager 120 via AP 111.

If mobile station 104 does not detect any AP then at 316, mobile station104 turns off or puts on “standby” wireless communication interface 210or portions thereof, where standby is a low-power mode in which themobile station is not associated with any access point. At 316, mobilestation 104 also activates wireless communication interface 220. At 318,mobile station 104 communicates with mobility manager 120 via PLMN 108.At 320, mobile station 104 starts maintaining presence signaling withmobility manager 120 via PLMN 108.

The presence signaling between mobile station 104 and mobility manager120 continues in the background through the available connection(whether through eWLAN 114, AP 111 or the cellular network PLMN 108).

FIG. 4 is a flowchart of an exemplary method in mobility manager 120 forestablishing a communication session with mobile station 104, accordingto embodiments of the invention. At 402, mobility manager 120 receivessignaling from IP PBX 118, the meaning of which is that a communicationdevice, for example, one of devices 112, 132 or 134, is trying toestablish a communication session with station 104. Alternatively, themobility manager 120 receives signaling from enterprise data server 119,the meaning of which is that a communication device, for example, one ofdevices 113, 134 or 135, is trying to establish a communication sessionwith station 104. At 404, mobility manager 120 checks whether station104 is connected to eWLAN 114, for example via AP 122.

If station 104 is connected to eWLAN 114, then at 406, mobility manager120 establishes the communication session with station 104 via eWLAN114. For example, mobility manager 120 signals IP PBX 118 (or enterprisedata server 119) to route the incoming communication session to station104 via eWLAN 114. If station 104 is not connected to eWLAN 114, then at408, mobility manager 120 checks whether station 104 is connected toanother WLAN, for example via AP 111. If station 104 is connected toanother WLAN, then at 410, mobility manager 120 establishes thecommunication session with station 104 via the other WLAN.

If station 104 is not connected to eWLAN 114 or AP 111, then at 412,mobility manager 120 attempts to inform mobile station 104 about theincoming communication session via PLMN 106, for example, by sending oneor more GPRS (general packet radio service) packets to mobile station104.

If at 414 mobility manager 120 receives signaling from mobile station104 that indicates that mobile station 104 has connected to eWLAN 114,the method continues to 406. Otherwise, if at 416 mobility manager 120receives signaling from mobile station 104 that indicates that mobilestation 104 has connected to AP 111, the method continues to 410.

If at 418, mobility manager 120 does not receive signaling from mobilestation 104 that indicates that mobile station 104 has connected to AP111, mobility manager 120 establishes the communication session withstation 104 via PLMN 108. For example, mobility manager 120 signals IPPBX 118 (or enterprise data server 119) to route the incomingcommunication session to station 104 via PLMN 108.

FIGS. 5 and 6 are a flowchart of an exemplary method in mobile station104 for handling an incoming communication session that arrives when themobile station 104 is not connected to eWLAN 114, according toembodiments of the invention. The method of FIGS. 5 and 6 may beexecuted by mobile station 104 from a state in which station 104 isconnected to PLMN 108 and maintaining presence signaling with mobilitymanager 120 by way of PLMN 108.

At 502, station 104 receives from IP PBX 118 signaling about an incomingcommunication session, for example, signaling sent by mobility manager120 via IP PBX 118 at 408 of the method of FIG. 4. In response, at 504,station 104 activates communication interface 220 to scan for a WLAN.

If at 506 station 104 finds one or more APs of eWLAN 114, then at 508,station 104 connects to one of the found APs, for example, AP 122. At510, station 104 establishes the communication session through AP 122,infrastructure 124 and IP PBX gateway 118 or enterprise data server 119,and updates mobility manager 120 to indicate that it is currentlyconnected to eWLAN 114.

If at 506 station 104 does not find any AP of eWLAN 114, then at 507,station 104 searches for other WLANs. If at 507 station 104 does notfind any other WLAN, then at 512, station 104 establishes thecommunication session through PLMN 106 and turns off or puts on standbywireless communication interface 210 or portions thereof. It should beunderstood that the order described herein for station 104 to search fora network to connect to is merely an example and that any other ordermay be used.

If station 104 loses connectivity with eWLAN 114 while handling thecommunication session via eWLAN 114, as shown at 514, the methodcontinues to 515 where station 104 updates its presence information withmobility manager 120, and then to 512. If the communication session isended without loss of connectivity, as shown in 516, the methodterminates.

If the communication session that is maintained by station 104 via PLMN108 is terminated, as shown at 520, then the method terminates.

If at 507, station 104 does find another WLAN, for example AP 111, themethod continues to 600 of FIG. 6. At 600, station 104 connects to AP111. At 602, station 104 establishes the communication session throughAP 111, PSDN 106, PSDN gateway 116, infrastructure 124 and IP PBXgateway 118 or enterprise data server 119, and updates mobility manager120 to indicate that it is currently connected to the other WLAN.

If station 104 loses connectivity with AP 111 while handling thecommunication session via AP 111, as shown at 604, the method continuesto 515 of FIG. 5 where station 104 updates its presence information withmobility manager 120, and then to 512. If the communication session isended without loss of connectivity, as shown in 520, the methodterminates.

If the communication session that is maintained by station 104 via AP111 is terminated, as shown at 606, then the method terminates.

FIGS. 7 and 8 are a flowchart of an exemplary method in mobile station104 for handling an outgoing communication session, according toembodiments of the invention. The method of FIGS. 7 and 8 may beexecuted by mobile station 104 from a state in which station 104maintains presence signaling with mobility manager 120 by way of PLMN108.

At 702, station 104 recognizes that a user of station 104 is initiatinga communication session to another communication device. The method thencontinues from 504 as in the method of FIG. 5.

Computer-executable instructions for managing communications such as inthe above-described methods may be stored on a form of computer readablemedia. Computer readable media includes volatile and nonvolatile,removable and non-removable media implemented in any method ortechnology for storage of information such as computer readableinstructions, data structures, program modules or other data. Computerreadable media includes, but is not limited to, random access memory(RAM), read-only memory (ROM), electrically erasable programmable ROM(EEPROM), flash memory or other memory technology, compact disk ROM(CD-ROM), digital versatile disks (DVD) or other optical storage,magnetic cassettes, magnetic tape, magnetic disk storage or othermagnetic storage devices, or any other medium which can be used to storethe desired instructions and which can be accessed by Internet or othercomputer network forms of access.

Although the subject matter has been described in respect to anenterprise communication system and its co-operation with othernetworks, this is merely an example. Embodiments of the invention areapplicable in any other system where two or more communication links canbe used to communicate with a mobile device. For example, mobile devicemay be able to communicate with PLMN base station 110 and with AP 111but may not be configured to communicate with eWLAN 114. In thisexample, simplified versions of the methods described in FIG. 3-8 may beused with respect to base station 110 and AP 111. In addition, asimplified version of the method described in FIG. 4 may be implementedin one or more servers (not shown) coupled to PLMN 108 and/or PSDN/PSTN106.

Although the subject matter has been described in language specific tostructural features and/or methodological acts, it is to be understoodthat the subject matter defined in the appended claims is notnecessarily limited to the specific features or acts described above.Rather, the specific features and acts described above are disclosed asexample forms of implementing the claims.

1. A method in a mobile communication device, the method comprising: transmitting presence signaling to a mobility manager via a cellular network; in response to recognizing that a user of said device is initiating a communication session to another communication device, activating a wireless local area network interface of said mobile communication device and searching for and attempting to establish a connection to a wireless local area network; and if a connection to a particular wireless local area network is established, transmitting updated presence signaling to said mobility manager via said particular wireless local area network.
 2. The method of claim 1, further comprising: establishing said communication session with said other communication device via said particular wireless local area network.
 3. The method of claim 1, further comprising: if said connection is lost, transmitting updated presence signaling to said mobility manager via said cellular network, establishing said communication session with said other communication device via said cellular network and reducing power consumption of said interface.
 4. A computer-readable medium having computer-executable instructions which when executed by a computer in a mobile communication device result in: transmitting presence signaling to a mobility manager via a cellular network; in response to recognizing that a user of said device is initiating a communication session to another communication device, activating a wireless local area network interface of said mobile communication device and searching for and attempting to establish a connection to a wireless local area network; and if a connection to a particular wireless local area network is established, transmitting updated presence signaling to said mobility manager via said particular wireless local area network.
 5. A mobile communication device comprising: a processor; a cellular communication interface coupled to said processor; a wireless local area network interface coupled to said processor; and a memory to store code which, when executed by said processor, causes said mobile communication device to transmit presence signaling to a mobility manager via a cellular network using said cellular communication interface and in response to recognizing that a user of said device is initiating a communication session to another communication device, to activate said wireless local area network interface and to search for and attempt to establish a connection to a wireless local area network, and if a connection to a particular wireless local area network is established via said wireless local area network interface, to transmit updated presence signaling to said mobility manager via said particular wireless local area network.
 6. The mobile communication device of claim 5, wherein said code, when executed by said processor, further causes said mobile communication device to establish said communication session with said other communication device via said particular wireless local area network.
 7. The mobile communication device of claim 5, wherein said code, when executed by said processor, further causes said mobile communication device, if said connection is lost, to transmit updated presence signaling to said mobility manager via said cellular network, to establish said communication session with said other communication device via said cellular network and to reduce power consumption of said interface. 